Method of making fans



1 943. F. H. 'SY'CHUBERIT 2,336,303

METHOD OF MAKING FFANS Filed Aug. 4, 1941 3 Sheets-SheeLLl INVENTOR. FRAN K H, SCHUBERT A'T' TORNEY Dec. 7, 1943. SCHUBERT 2,336,303

METHOD OF MAKING FANS Filed Aug. 4, 1941 3 Sheets-Sheet 2 INVENTOR.

FRANK H. SCHUBERT BY ATTORNEY' Deg:- 7, 1943. F. H. SCHUBERT METHOD OF MAKING FANS Filed Aug. 4, 1941 s Sheets-Sheet a INVENTOR. FRANK H. SCHUBERT I ATTORNEY FLGLZZ.

Patented Dec. 7, 1943 UNITED snares PATENT OFFICE.

METHOD OF MAKING FANS Frank H. Schubert, St. Louis County, Mo.

Application August 4, 1941, Serial No. 405,346

1 Claim.

This invention relates generally to fluid propulsion devices, such as fans, propellers, and the like, and, more particularly, to certain new and useful improvements in methods for making the same.

It is a primary object of my invention to provide a method of making a fan composed of two or more uniquely constructed and designed blades having a highly eflicient contour and cross-sectional shape, and which may be readily adapted to meet any requirements of pitch distribution by simple modification of peripheral contour.

, It is a further object of my invention to provide a method of making a plural-bladed fan or propeller which is extremely efficient and economical in construction, which is inherently balanced both statically and dynamically, and which does not require extensive balancing operations after the blades are initially formed.

It is an additional object of my invention to provide a method for making fan blades of the type stated which is simple, efiicient, and economical, which enables the use of relatively inexpensive materials, and which results in the production of inherently matched sets of blades which may be quickly and conveniently assembled in the formation of a statically and dynamically balanced fan or propeller.

And with the above and other objects in view, my invention resides in the novel features of form, construction, arrangement, and combination of parts and in the unique steps of production presently described and pointed out in the claim.

In the accompanying drawings (three sheets),

Figure l is a perspective view of a tubular metallic section or so-called blank from which a set of fan-blades may be manufactured in accordance with my present invention;

Figure 2 is a perspective view of the tubing section initially slit or divided in the process of manufacturing a set of fan-blades in accordance with my invention;

Figures 3 and 4 illustrate, in perspective, and end elevation, respectively, a blade of my invention being subjected to an initial edging operation in a milling machine specifically adapted for such purpose;

Figures 5 and 6 are fragmentary side and front elevational views, respectively, of a uniquely constructed milling machine for forming any desired contour along the longitudinal margins of the fan-blade;

Figure 7 is a plan view of a fan-blade constructed in accordance with and embodying the present invention;

Figures 8, 9, 10, and 11 are transverse sectional views of the fan-blade taken approximately along the lines 88, 99, llllll, and I |--I I, respectively, Figure 7;

Figures 12 and 13 are front and side elevational views, respectively, of a hub-member forming a part of the fan-blade of my present invention;

Figures 14 and 15 are front and side elevational views, respectively, of a four-bladed fan constructed in accordance with and embodying my present invention;

Figure 16 is a fragmentary sectional view taken approximately along the line I6I6, Figure 15;

Figure 17 is a perspective view of a tubular section longitudinally slit or cut to form a matched set of three blades in accordance with my present invention;

Figure 18 is a front elevational view of a threebladed fan constructed in accordance with my present invention;

Figures 19, 20, and 21 are front elevational views of six, two, and eight-lugged hubs, respectively, for use in the construction of further modified forms of fans; and

Figure 22 is a plan view of a modified form of fan-blade of my invention in which both the leading and trailing edges have been contoured to achieve a desired type of pitch distribution.

Referring now in more detail and by reference characters to the drawings, which illustrate practical embodiments of the present invention, A designates an elongated cylindrical section or so-called blank of drawn seamless tubing preferably of steel or any other suitable material and having a length and diameter selected with reference to the particular characteristics which are desired in the finished fan, such, for instance, as the speed of rotation, finished fan diameter, character of the fluid medium in which the fan is operating, quantity of such fluid medium which must be'moved in a given unit of time, and the static pressure against which the fluid medium must be de ivered.

As will be presently more fully explained and pointed out, my present invention enables the manufacture of fans having two or more blades, although, for purposes of illustration, the meth- 0d of making a four-bladed fan of my invention will be initially described.

Accordingly, the tube A is cut lengthwise or axially by means of any suitable slitting saw or other cutting instrument into four equal or quatro-cylindrical segments a, each, in turn, forming or providing a blank for a single or individual blade. In this connection, it should be noted that drawn seamless tubing is ordinarily of substantially uniform thickness, texture, and density throughout its length, as a result of the metal-working process by which it is made, and, by reason of such processes, lends itself to a fairly high degree .of precision, the circularity, concentricity, and uniformity of wall thickness of such tubing being precise within relatively close tolerances. In any case, variations in any of such particulars, such as uniformity of wall thickness, circularity, or density of metal, are

For exam-- substantially annular in character. ple, if there is any deviation in-wa-ll thickness of the tubing, such deviation will occur as a ring-like increase in mass around the entire circumference of the tubing. It is, therefore, desirable that, prior to cutting, the tubing A should be marked at one end by an annular ring of paint, chalk, or other eradicable means, so:that, when the segments or blanks a have been segregated, the ends which were normally co-incident in the original tubingsectionA may be identified and the segments or. blanks a subsequently machined with reference to such marked end. Thus any variations in thickness or density of the metal will occur at the same occur at identical relative distances from the blade-tip in each blade, obviating dynamic distortion or imbalance and resulting in a set of blades having inherent dynamic balance.

Each of the segments or blanks a is then placed in an edging machine B, which includes a horizontally disposed spindle I provided at its outer end with a suitable hob or cutter 2 having a preferably semi-circular cutting groove-3, Suitably mounted upon the bed of the .-machine B for straight line horizontal movementbeneath the cutter 2, is a suitably shaped work carriage 4 having an oblique work-supporting face-ii and suitable work clamps E for securing the blank or segment a, horizontally upon the carriagel withits one longitudinal margin. in upwardly presented alignment with the cutting groove 3, so that, as the carriage 4 is reciprocatedbe neath the cutter 2, a semi-circular or roundedoif leading edge L will be machined along such upwardly presented longitudinal margin, all as best seen in Figures 3 and 4.

With the accurately machined leading edge L as a point of reference, a suitably shaped bladepattern (not shown) is laid' upon the blank a and the contour of the trailing edge marked off. The contour of the trailing edge may, of course, be designed to achieve any desired pitch distribution along the length of the blade and may followany appropriate curve indicated by the design requirements of the particular blade.

The trailing edge is then rough-cut by any suitable method to remove substantially all of the excess metal.

Thereupon the blank ais placed in a contouring machine C, which includes a vertically disposed spindle 1 provided at its lower end with a hob or cutter 8 having a deep tapering cutting groove!) of 'such' cross-sectional'shape as to form a trailing edge T of substantially feathered cross-sectional shape, Slidably mounted upon the bed of the machine C for shiftable movement horizontally beneath the cutter 8, is a work-carriage ill having a vertically disposed apron H provided upon its inner face with a pair of spaced parallel ways or slots i2, slidably mounted in which are pivot-blocks i3 having studs id projecting outwardly through the apron H to receive at their outer ends clamping-nuts 15 for holding the blocks H3 at any selected position of vertical adjustment upon the apron l i.

Swingably mounted upon the blocks [3 by means of axially aligned pins E5, the centers of which are substantially in vertical alignment with the efiective face of the cutting groove 9 of the hob 8, is a jig ll provided upon its outer end with a flange i8 having an outwardly presented arcuate work-engaging face l9. Formed integrally with, and disposed outwardly from, the flange it at conveniently spaced points therealong,. are upwardly extending brackets 28 provided with radially extending clamping screws 2! for rigidly holdinga blade-blank a in place against the work-face I9.

Also formed integrally with the jig-flange l8 preferably midway between its ends, is a depending bifurcated bracket 22 provided with a trans- Verse pin 23 for supporting a guide roller 2% adapted to engage the upwardly presented margin 25 of a templatezi, which is horizontally supported by means of bolts 21 between a pair of spaced horizontal arms 28, in turn, fixed upon a suitable upright portion of the framework of the machine C.

The template 25 is an axial segment of a cylinder having the same diameter and thickness as the blank a and is positioned so as to have its :risof curvature coincide with the axis of rotation of the jig H, the upwardly presented longitudinal margin 25 of the template 26 being accurately machined to a curve which is the mirrorimage of'tlie desired curve to which the roughedout peripheral margin of the blank a is to be machined for the formation of the trailing edge T.

It will, ofcourse, beundersto-od that the particular template ZS may be changed from time to time as the designof the trailing edge curve is changed-to provide fan-blades having the particular calculated characteristicsnecessary to meet the requirements of a particular use or installation. Thus, when an appropriate template 26 is properly mounted upon thearms 28, the roller 26 of the jig I1 will rest-upon the upwardly presented or so-called curved generating margin 25 of the template 26.

When a blank a is properly mounted and clamped in the jig l7 and the carriage Iii shifted horizontally along thebed of the machine C, the

particular template 26 will rock the blank or work arcuately about its own cylindric'alaxis toward and away from the cutter 8 for accurately machining a trailing edge T having the desired curved conformation.

The blank a is then removed from the machine C and the root or hub-engaging end portion r is provided withtwo axially spaced tranfiverselyextending closed-ended slots, as at s, and preferably, though not necessarily,- beveled; as at b, and inscribed upon such beveled face adjacentits transverse margin with a series of graduations g in the provision of a completed blade D l The several other blanked out fromthe original section A are likewise machined and finished in precisely the same manner, care being taken to clamp theseveral blanks a inlthe contouring machine C in such a manner that the marked ends of each blank will bear the same relative position in each case to the template 26, a matched set of four blades resulting.

In this connection, it should be noted that the preferred form of blade D is truly circular in transverse or cross-sectional shape throughout its length, as shown in Figures 8, 9, and 10. The length of the circular are along any transverse line, as for example, shown in Figure 9, will always bear a definite and mathematically calculable relation to the angle of pitch of such section which, for the theoretical ideal blade, may be stated in the following formula wherein Z is the length of the arc, R is the radius of the cylindrical section, and is the angle of pitch. In actual practice, it may be necessary to modify somewhat the pitch distribution curve of a given blade by an experimentally determined coefficient to compensate for degree of turbulence, percentage of slip, adiabatic friction, and other unpredictable factors. For this reason, the blade is highly efficient and lends itself readily to substantially any variations in pitch distribution imposed by design requirements of the particular use for which the particular fan is constructed.

Referring now particularly to Figures 12 and 13, H designates a preferred form of hub element, which integrally includes a tubular sleeve 29 axially drilled in the provision of a shaft-receiving bore 38 and radially bored and tapped in the provision of a set-screw receiving aperture 30. Upon its outer face adjacent one end, the sleeve 29 is preferably integrally provided with four equally spaced radially extending arms 3| each having an outwardly presented blade mounting face 32 accurately machined to conform to the segment of an arcuate surface having the same radius of curvature as the hub portion R of the respective blades D. Preferably, though not necessarily, the blade mounting faces 32 of the several arms 3| are angularly oriented with reference to the axial line of the hub-sleeve 29, so that the axes of curvature thereof will lie in a common plane spaced rearwardly from the arms 3| and disposed at 90 to the axis of the hubsleeve 29, and, in addition, the several axes of curvature of the blade mounting faces 32 will not be truly radial to the hub sleeve 29, but will be disposed in spaced parallel relation to the radial axes of the respective arms 3|, as best seen in Figure 13.

Each of the arms 3| is further provided with a pair of radially spaced threaded drill-holes 33 positioned so that their axes are precisely radial to the blade mounting face 32, and finally each blade mounting face 32 is inscribed or otherwise provided with an index-line or indication m as a reference point for the graduated scale 9 on the blades D.

In completing the assembly of the fan, the four matched blades D are secured against the blade mounting faces 32 of the hub arms 3| by means of suitable bolts 34, substantially as shown in Figures 14, 15, and 16. Prior to tightening down the bolts 34, each blade D is accurately adjusted and set as to pitch by careful rotation about its longitudinal axis so as to slide the root portion R. over the face 32 of the hub arm 3| until a selected graduation of the scale 0 is aligned with the index mark m, whereupon the bolts 34 are securely tightened down.

be mounted upon an eight-arm hub h.

a fan having any multiple of three or four blades 7 Since all of the blades D in the matched set are formed from a single piece of seamless drawn tubing and are accurately contoured from the same template, the curvature, mass-distribution, aspect-ratio, and pitch-distribution will be identical. And, finally, since the scale 9 on each blade is identical, all the blades D, when set to the same selected graduation, will have identical pitch. Consequently the fan thus produced will be very accurately balanced, thereby substantially eliminating the conventional cut-and-try" balancing methods which have been necessary without exception in the manufacture of all fanblades heretofore, so far as I am aware.

Now, further, Adesignates a section of seamless drawn tubing cut into three blank-forming segments a, each of which may be contoured in the manner and by the means above described to the pattern indicated in dotted lines to form a matched set of three blades D. Provided, also, for assembly with the set of blades D, is a hub H, substantially identical in all respects with the hub I-I, except that the former is provided with three arms 3| instead of four arms 3|. The blades D' are bolted or otherwise suitably secured upon the hub H and set for pitch, as previously described, in the formation of a three-bladed fan, as shown in Figure 18.

If desired, a six-bladed fan may readily be constructed by superimposing a second matched set of three blades D upon a first set of blades D, as illustrated in dotted lines in Figure 18.. Obviously the second set may be secured upon a separate hub H and separately keyed to a suitable driving shaft, so that the blades D" lie midway between the blades D, or a suitable sixarm hub it may be provided, so that both sets of iblades may be mounted on a single hub strucure.

Similarly, where a two-bladed fan is desired, a matched set of four blades D, such as described, may be divided to provide two pairs of matched blades for two such fans, a suitable two-arm hub h being employed for such purpose.

On the other hand, if an eight-bladed fan is desired, two matched sets of four blades D may In fact,

may be constructed employing an appropriate number of matched sets, provided only that the particular blades of each such set be arranged equidistantly from each other so as to preserve their inherent dynamic balance.

It may be added that, where rather extreme degrees of pitchdistribution are required, my invention facilely enables the production of a blade D having a suitably shaped protruding curve along its leading edge, as shown in Figure 22, and which is constructed in substantially the manner previously described, except that both the leadin and trailing edges are necessarily contoured in a contouring machine C by the use of suitably shaped templates.

Finally, it will be apparent that my present method and apparatus are equally well suited to the formation of blades from tapered, as well as cylindrical, tubing and from tubing having modified cross-sectional shapes, and it should also be understood that changes and modifications in the form, construction, arrangement, and combination of the several parts of the fans and in the apparatus and method for making the same may be made and substituted for those herein shown and described without departing from the nature and principle of my invention.

set of balanced and matching screw-type blades formed from a single lengthof cylindrical hollow tubing of selected size which tubing is of substantially the same general: thickness throughoutxits length and periphery but of non-uniform density throughout its length, which comprises dividing the cylindrical wall throughoutits length at uniiormly equally spaced points vlongitudinally 'into a plurality of :Vcompanion' like segments; .arcuate 2 segments into ablade base, contouring the edges of the remaining part of each segment substantially identically as a screw-type blade, whereby the corresponding peripheral portions of the original-wall of the hollow tube Will be in substantiallythe same spacing from the center of'rota- 7 tion' when said blades are incorporated in an im peller, rou'ndingoff alike the leading edge of each ing margin of each segment, and mounting such circu'mferentiallyabout a hub. H. SCHUBERT. 

